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    <title>
        Document
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    <style>
        .box {
            width: 100px;
            height: 100px;
            background-color: cyan;
            /* border-radius-left-top: 50%; */
            border-top-left-radius: 100px;
        }
    </style>
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<body>
    <div class="box"></div>
    <iframe src="//player.bilibili.com/player.html?aid=58761546&cid=102457433&page=43" scrolling="no" border="0"
        frameborder="no" framespacing="0" allowfullscreen="true"> </iframe>
    <script>
        var a = ['zd', 'qe']
        var o = {
            name: 'asd',
            age: 12
        }
        // 1. typeof
        // typeof 只能简单的判断出 Object，数组和对象 都属于 object

        // 2、instanceof 
        console.log(a instanceof Array) // true
        console.log(a instanceof Object) //true
        console.log(o instanceof Array) // false
        console.log(o instanceof Object) //true

        //3、 constructor 访问对象类型，访问对象的构造函数
        console.log(a.constructor) // ƒ Array() { [native code] }
        console.log(o.constructor) // ƒ Object() { [native code] }      

        //4、 toString(), Object.prototype.toString()
        console.log(Object.prototype.toString.call(a)) // "[object Array]"
        console.log(Object.prototype.toString.call(o)) // "[object Object]"
    </script>
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